This invention relates to an apparatus for cleaning a recording medium and more in particular to a cleaning apparatus for removing color particles, such as toner, which remain on the surface of a recording medium after image transfer thereby preparing the medium for the next cycle of operation.
Described more specifically, in electrophotography or electrographic recording, on a recording medium is formed an electrostatic latent image, which is then developed by color particles such as toner, magnetic or non-magnetic, to form a developed, visible image, which, in turn, is transferred to a transfer material, thereby obtaining a copy of an original image. However, since some toner particles remain on the surface of the recording medium after image transfer, the surface of the recording medium must be cleaned or the residual toner particles must be removed in order to prepare for the next cycle of operation. The present invention is concerned with a cleaning apparatus to be used in such circumstance. 2. Description of the Prior Art
An apparatus for cleaning the surface of a recording medium after image transfer is well known in the art. One such prior art cleaning apparatus is comprised of a non-magnetic sleeve, on the outer surface of which is planted short fibers, and magnets disposed inside of the sleeve. For example, use is made of aluminum to form a non-magnetic sleeve, and a fiber material having the thickness ranging approximately from 0.3 mm to 1 mm, the fiber material being made of synthetic fibers, such as nylon and rayon, of natural fibers, such as cotton and wool, or of conductive fibers, such as carbon or metal, is adhered to the outer surface of the sleeve, which is then rotatably disposed with a gap ranging approximately from 0.2 mm to 0.5 mm between the outer surface of the sleeve and the surface of the recording medium, whereby the fiber material is pressed over a distance ranging approximately from 0.1 mm to 0.5 mm. Since the sleeve is rotated under the condition, residual toner on the surface of the recording medium is removed and, therefore, the medium is cleaned and made ready for use in the next cycle of operation. In the case of one-component or magnetic toner particles, they are attracted to the outer surface of the sleeve due to magnetic forces exerted by the magnets disposed inside of the sleeve. Thus, cleaning of magnetic toner particles is carried out in two-fold--mechanical scraping or separation of particles from the recording medium by fibers and magnetic attraction of particles toward the outer surface of the sleeve. As the sleeve rotates, the toner particles collected on the outer surface of the sleeve are carried to a desired location.
In a cleaning apparatus of the type described above, it is important to maintain the gap between the sleeve and the recording medium at constant in order to attain an excellent cleaning performance. Stated in another way, the contact between the fabric material adhered to the sleeve and the surface of the recording medium must be held uniformly or invariably throughout cleaning operation. Otherwise, irregularities in cleaning result so that some residual toner particles remain unremoved, which will provide adverse effects to the next cycle of operation. For this reason, one prior art approach to cope with this problem is to provide a pair of bearings having the outer diameter slightly larger than that of the sleeve on both ends of the sleeve. With such a structure, the sleeve is rotated with the bearings in contact with the surface of the recording medium so that the gap between the sleeve and the recording medium may be maintained at constant. However, such a structure is rather complicated and thus tends to be expensive. More importantly, when toner or other foreign matter is stuck to the bearings or to that portion of the recording medium which comes into contact with the bearings, the gap between the sleeve and the recording medium will fluctuate thereby bringing about irregularities in cleaning performance.